Etymology Dictionary

ALONG,  lengthwise of.  (E.)   [The prefix here is very unusual, as the a- in this case arose from the A.S. and-; see A-, prefix; and see Answer.]   M.E. along, Allit. Poems, ed. Morris, B. 769; earlier anlong, Layamon, i. 7.—A.S. andlang, along, prep. governing a genitive; 'andlang þæs wéstenes' = along the waste, Joshua, viii. 16. + O. Fries. ondlinga, prep. with gen. case; as in 'ondlinga thes reggis' = along the back (Richtofen). + G. entlang, prep. with gen. or dat. when preceding its substantive.—A.S. prefix and-, cognate with O. Fries. ond-, O.H.G. ant- (G. ent-), Goth. and-, anda, Lat. ante, Gk. ἀντί, Skt. anti, over against, close to; and A.S. adj. lang, long.   The sense is 'over against in length.'   See Long.   ¶ We may also compare Icel. adj. endilangr, whence the adv. endelong, lengthwise, in Chaucer, C. T. 1993. [†]

ADDENDA

The note, in the former edition, that E. along is different from Icel. endilangr is wrong.   Dr. Murray remarks that the A.S. andlang was at first an adjective, and afterwards a preposition, and that, as an adj., it is precisely the Icel. endilangr or endlangr, i.e. all along, throughout the length.   See A.S. andlang in Bosworth's A.S. Dict. (new edition).   The M.E. endelong was a modification of A.S. andlang, due to confusion with ende (end), and loss of the sense of the prefix.   Yet it is not altogether wrong, for the connection between end and the prefix and- is real; see End.   Along is, in fact, anti-long or end-long (taking end in the sense of parallel edge), side by side.